- A
The LCD panel itself
Why wrong: A failing panel would typically show distorted images, lines, or dead pixels, not uniform dimness.
- B
The inverter board
The inverter supplies high voltage to the CCFL backlight; when it fails, the backlight dims or goes out entirely.
- C
The video cable
Why wrong: A faulty video cable would cause signal issues like artifacts or no display, not uniform dimness.
- D
The power supply unit
Why wrong: A failing PSU would cause the entire computer to shut down or restart, not just affect display brightness.
Question 426 of 1,020
Diagnosing a Dim LCD Monitor: CCFL Backlight Inverter Failure
This 220-1201 practice question tests your understanding of display devices. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user reports that their desktop computer's display is very dim, even at maximum brightness settings. The monitor is an older LCD model with a CCFL backlight. What component is most likely failing?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Quick Answer
The answer is the inverter board. This component is the most likely cause of a dim LCD monitor with a CCFL backlight because it converts the system’s low-voltage DC power into the high-voltage AC required to illuminate the fluorescent tube; when the inverter fails, it cannot supply enough voltage, resulting in a very dim display even at maximum brightness settings. On the CompTIA A+ Core 1 220-1201 exam, this question tests your knowledge of display technologies and common hardware failures, often appearing as a troubleshooting scenario where you must distinguish between a failing backlight inverter and a faulty power supply or video cable. A common trap is confusing the inverter with the backlight itself—remember that the tube rarely fails first, while the inverter board is the weak link in older monitors. Memory tip: think “inverter = voltage converter” for the CCFL’s high-voltage hunger.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The inverter board
The inverter board is responsible for converting DC power from the power supply into the high-voltage AC required to drive the CCFL (cold cathode fluorescent lamp) backlight in older LCD monitors. When the inverter fails, the backlight either dims significantly or fails entirely, even though the LCD panel itself may still be receiving a valid video signal and the brightness controls appear to function. This matches the symptom of a very dim display at maximum brightness settings.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The LCD panel itself
Why it's wrong here
A failing panel would typically show distorted images, lines, or dead pixels, not uniform dimness.
- ✓
The inverter board
Why this is correct
The inverter supplies high voltage to the CCFL backlight; when it fails, the backlight dims or goes out entirely.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The video cable
Why it's wrong here
A faulty video cable would cause signal issues like artifacts or no display, not uniform dimness.
- ✗
The power supply unit
Why it's wrong here
A failing PSU would cause the entire computer to shut down or restart, not just affect display brightness.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA A+ often tests the misconception that a dim display is always caused by a failing LCD panel or a bad video cable, when in fact the backlight subsystem (inverter or CCFL) is the most likely culprit in older monitors with CCFL technology.
Trap categories for this question
Command / output trap
A failing panel would typically show distorted images, lines, or dead pixels, not uniform dimness.
Detailed technical explanation
How to think about this question
CCFL backlights require a high-voltage AC signal (typically 600–1000V at 30–80 kHz) to ionize the gas inside the tube and produce ultraviolet light, which then excites the phosphor coating. The inverter board uses a transformer and a driver IC (e.g., OZ960 or TL494) to step up the DC voltage; a common failure mode is a cracked transformer winding or a failed capacitor that reduces the output voltage, causing the backlight to dim. In a real-world scenario, a technician might confirm inverter failure by measuring the output voltage with a multimeter or by observing that the backlight briefly flashes on startup before going dim.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Display Devices — This question tests Display Devices — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The inverter board — The inverter board is responsible for converting DC power from the power supply into the high-voltage AC required to drive the CCFL (cold cathode fluorescent lamp) backlight in older LCD monitors. When the inverter fails, the backlight either dims significantly or fails entirely, even though the LCD panel itself may still be receiving a valid video signal and the brightness controls appear to function. This matches the symptom of a very dim display at maximum brightness settings.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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